Now you can create simple rules that will filter/transform the tags when adding new books or downloading metadata for books. To setup the rules, go to Preferences->Adding books and Preferences->Downloading metadata

Kobo driver: Support for newly firmware version 3.18

Edit Book: Add a setting to control icon size for the toolbars (Preferences->Toolbars)

A new tool to apply Tag mapper rules to existing books in the library. To use it, go to Preferences → Toolbars and add the tool to the toolbar.
Kindle driver: Detect books in Amazon's new KFX format present on e-ink kindles.

Note that this only detects KFX books and allows you to delete them. You cannot copy them to your calibre library. Doing so would be pointless anyway, as KFX books are specialised for individual devices. Instead go to your ‘Manage my content’ page an amazon.com and download them from there — this will give you a regular azw3 file you can add to calibre.

Bug Fixes

TXT Output: Do not fail when input contains HTML comments with double hyphens in the comment text.

E-book polishing: Show a confirmation if the user selects both the add and remove jacket actions.

Edit Book: Fix order of checkboxes in filter style information tool is random

PDB Input: Ingore malformed metadata records.

Revert change in previous release to workaround broken xdg-open on linux. Apparently xdg-open is so badly broken that working around it is not possible.

ZIP Output: Fix system encoding being used instead of UTF-8 for html files.

Press Ctrl+` to trigger the tool, or add the tool to your toolbar via Preferences->Toolbar->Tools for all editors. It will either insert comments around the selected text or uncomment an existing comment if the cursor is inside one.

Markdown input: Allow the 'extra' convenience extension as a shortcut for enabling multiple other extensions. Also add the Attribute List and Admonition extensions. Finally, update the markdown library used by calibre

Bug Fixes

Amazon metadata download: Fix for website change at amazon.com that prevented ratings from being downloaded.

Tag mapper: Prevent cycles in the replacement rules from causing the tag mapper to hang

Do not fail on windows systems where the system function to get the users home folder fails

E-book viewer: Set the foreground color as well as the background color for the reference mode popup. Makes it legible even when the user specifies a different color theme for the viewer.

A new tool to easily export and import all calibre data – books, settings and plugins

Right click the calibre icon in the main calibre toolbar and choose "Export/import all calibre data" to run this tool. It is useful if you want to move to a new computer or duplicate your calibre setup on a second computer, with minimal effort. This tool is very new, so if you run into problems, please report bugs. You can always use the old manual method of copying library folders as a fallback.

Get Books: Add plugins for Amazon Australia and Amazon India. Also restore the Amazon EU plugins.

Bug Fixes

PDF Input: Fix conversion of PDF documents that contain ASCII control codes in their outlines not working.

E-book viewer: Make the detection of note boundaries for popup footnotes a little more robust

E-book viewer: Add options to control the amount the mouse wheel and arrow keys scroll by in flow mode

When running the content server do not hide the main calibre window during shutdown until the content server has stopped. Show a shutting down message in the window so that the user knows what is happening.

Edit Book: Check Book: Add a check for empty links

DOCX Input: When the document has a Table of Contents created using the Word Table of Contents tool, keep a reference to it in the metadata. This is useful when converting to old style MOBI and you want to precisely control placement of the ToC.

Bug Fixes

Fix auto-mounting of some types of devices not working on FreeBSD

calibredb add: Fix the --cover option not working if the book being added has its own cover.

E-book viewer: Fix mathematics being typeset at too small a font size on windows

PDF Output: Fix occasional blank pages erroneously inserted in the text (at the end of an internal html file).

Book details panel: Fix url:file:// identifiers not becoming links

Fix fetch news dialog not rendering properly on HiDPI screens

Fix a hard to trigger crash introduced in the previous release when using the conversion dialog

Edit Book: Add an option to show full file paths in the Files Browser instead of just the file name (in Preferences->Main window)
Allow creating a keyboard shortcut to minimize the calibre window (Preferences->Keyboard->Miscellaneous).

Bug Fixes

Fix the Google Images based cover download plugin not working because of changes to Google's image search service

OS X: Redirect stdout/stderr to /dev/null instead of ASL since ASL is flaky on some OS X machines. This should prevent errors in third party plugins that print a lot of debug messages even when not in debug mode